Under terms of the deal, Pfizer will acquire rights to Encysive's pulmonary arterial hypertension (PAH) treatment Thelin (sitaxsentan sodium), which is already available in the UK and Europe Union, Australia and Canada. In the US, Thelin has been the subject of three approvable letters from the FDA. Pfizer plans to conduct a pivotal Phase III trial to support registration in the US.

“The acquisition of Encysive will add growing, near-term revenue from the European market and increase our already strong presence in the cardio-respiratory arena with a product that complements Revatio, a PAH treatment that was discovered and developed by Pfizer researchers," said Ian Read, president of Pfizer's worldwide pharmaceutical operations. "We look forward to applying Pfizer's significant resources to the launch of Thelin in additional countries."

PAH is a progressive, incurable disease that is estimated to affect 100,000 to 200,000 people in North America and Europe, including about 55,000 persons in the US.